Electrical control mechanism



Aug. 22, 1950 A. F. REHNBERG HAL ELECTRICAL CONTROL ECHANISII 3 Sheets-Sheet 1 Filed April 24, 1946 A. F. REHNBERG m-AL 2,520,014 ELECTRICAL CONTROL KECHANISII Aug. 22, 195o 3 Sheets-Sheet 2 Filed April 24, 1946 VV y /7 H1 9 Q M Nm. nm,

Aug. 22, 1950 A. F. REHNBERG :TAL 2,520,014

ELECTRICAL coNTRoL uEcHANrsu Fi-led April 24, 1946 3 Sheets-Sheet 3 ELECTRICAL CONTROL MECHANISM Axel F. Rehnberg and John Nelson, Rockford, Ill., assignors to Rehnberg-Jacobson Mfg. Co., Inc., Rockford, Ill., a corporation of Illinois Application April 24, 1946, Serial No. 664,468

14 Claims. (Cl. 192--116.5)

This invention relates to an electrical control mechanism for machine tools.

Hydraulic control mechanisms used heretofore were operated on the principle of varying the amount of oil injected into the working cylinder behind the piston connected to the machine tool carriage to be moved. There have, however, been several serious criticisms of these hydraulic vcontrol mechanisms, and, as a result, machine tool builders have in recent years been looking for some other solution to the problem. It is, therefore, the principal object of our invention to provide an electrical control mechanism which is simple and economical in construction and thoroughly practical and widely adaptable in its application.

In the mechanism of our invention, a feed screw that is held against endwise movement relative to the bed of the machine has an elongated splined portion next to its fixed end on which a splined sleeve is slidable that is arranged to be driven by a reversible electric motor for rapid approach and return, a nut threaded on the screw and arranged to be driven by a series-wound electric motor operable by electrical control at any selected speed within a predetermined range being provided to obtain whatever feed is desired. Both motors, in accordance with our invention, are mounted on the carriage for greater compactness and to enable shortening the overall length of the machine for a given travel of the carriage, thereby also improving the appearance of the machine as a whole and lowering the cost.

Another important object of our invention is to provide a novel control box in which a cam is reciprocable to operate a plurality of switches to control the starting and stopping of the two motors mentioned above and the reversing of the iirst mentioned motor, and in which there is also a rheostat for control of the speed of the other motor, the stem of the rheostat being turned by means of a rack and pinion operable by means of a plunger movable like the aforesaid cam by dogs in the movement of the carriage, the -plunger tending to move downwardly by gravity toward a limit position and a corresponding top speed of the motor for which a limit screw limiting the drop of the plunger is set, lower speeds being obtained by dog movement of the plunger upwardly. This permits sudden step-ups or step-downs in feeding speeds, as for example, a step-down from a feed speed suitable, let us say, for drilling to a lower feed speed suitable, let us say, for a facing operation.

The invention is illustrated in the accompanying drawings, in which Fig. 1 is a longitudinal section through the carriage and a portion of the bed of a. machine, such as a multiple spindle drilling and facing machine, embodying electrical control mechanism made in accordance with our invention;

Fig. 2 is a view partly in plan and partly in horizontal section on the line 2--2 of Fig. 1;

Figs. 3 and 4 are sectional details in planes at right angles to one another of the control box which appears in horizontal section on a smaller scale in Fig. 2, and

Fig. 5 is a wiring diagram.

The same reference numerals are applied to corresponding parts throughout these views.

Referring first mainly to Figs. 1 and 2, the

reference numeral E designates the bed or base portion of the machine on one end of which a housing I is fixed to provide radial and end thrust bearing support for one end of the feed screw 8, as indicated at 9. The feed screw 8 has an elongated splined portion IU next to its fixed end on which a splined sleeve II is slidable, the latter having radial and end thrust bearing support in one end of a housing I2, as shown at 'I3. A nut I 4 is threaded on the feed screw and has radial and end thrust bearing support in the other end of the housing I2, as indicated at I5. The housing I2 is mounted in the carriage I6 which supports the electric motor or motors I'I that drive the spindle or spindles connected to the drills, tags, reamers, milling cutters, or whatever tools are to be operated. A single spindle is indicated at I8 connected through a coupling I9 with the armature shaft 2U of the motor II, but it is understood that the spindle I8 may drive one of a cluster of gears connected to the several tools to be driven.

In accordance with our invention, rapid traverse, forward or reverse, is obtainable by driving the feed screw 8 with the sleeve II in the proper direction by operation of the reversible electric motor 2|, and different feeds are obtainable by driving the nut I4 at different speeds with the series-wound electric motor 22. The motor 2 I, which is adjustably pivotally mounted on one end of the carriage I6, has a pulley 23 on its armature shaft over which a belt 24 extends to drive the pulley 25 fixed on the outer end of a shaft 26. The latter is disposed horizontally in transverse relation to the splined end I0 of the feed screw and supported in bearings 2l in the carriage I6. A worm 28 keyed on the shaft 26 meshes with a worm gear 29 that is secured to the sleeve I I. The motor 22, which is adjustably pivotally mounted on the other end of the carriage I6, has a pulley 30 xed on the armature shaft thereof, and has a belt 3I extending over it to transmit drive to a. pulley 32 fixed on the outer end of another shaft 33. The latter is disposed horizontally in transverse relation to the feed screw 8 and mounted in bearings 34 in the carriage. Another worm 36 keyed on the shaft 33 meshes with a worm gear 36 that is secured to the nut I4. The carriage I6, carrying the motor or motors I'I and the motors 2| and 22, is guided for reciprocatory movement on ways 31 provided on the base or bed 6 of the machine and moves through a predetermined distance, as indicated, for example. by the carriage positions labelled Pos. #1"Pos. #4" in Fig. 1. The forward movement of the carriage is positively limited by engagement with a positive stop, which may be suitably adjusted. Thus, for example, the head of a screw 38 on the forward end of the carriage is arranged to engage the rear end of a set screw 39 adjustably threaded in the boss 40 provided on the front end of the bed 6.

In operation, the conventional cycle of rapid traverse forward, feed and rapid traverse reverse is obtainable with the present construction as follows:

1. The motor 2| is operated in a forward direction to drive the sleeve II for rapid approach movement of carriage I6 from Pos. #1 to Pos. #3 and then is stopped. The feed screw 8 in this operation is turned relative to the nut I4 to move the carriage I6 forwardly, and the sleeve l I slides forwardly on the splined portion Il) of the feed screw 8 as the sleeve moves forward with the carriage.

2. The motor 22 then drives the nut I4 at a slow speed relative to the feed screw 8 to move the carriage I6 forwardly at a feed rate through a predetermined distance from Pos. #3 to Pos. #4 and then stops, the sleeve Il in this movement sliding forward on the splined portion I0 of the feed screw.

3. The motor 2|, running in the reverse direction, drives sleeve I I to turn the feed screw 8 in the reverse direction relative to the nut I4 for rapid return of carriage I6 from Pos. #4 to Pos. #1, and then stops.

In accordance with our invention, we obtain whatever feed is desired by electrical control of the speed of the motor 22. A control box is indicated at 4I in Fig. 2, mounted on the side of the carriage I6. It contains a gravitating rack plunger 42 that is vertically reciprocable by dog operation of its beveled lower end 43, and also a cam plunger 44 that is vertically reciprocable by dog operation of its lateral projecting roller 45. It is obvious from Fig. 3 that one set of dogs arranged in one line a-b extending longitudinally of the bed 6 may operate the one plunger, an another set of dogs arranged in another parallel line c d on the bed 6 may operate the other plunger. ,Thus dogs 59, B0 and 6I 'are in the inner line c-d to operate plunger 44, and dog 62 is in the outer line a-b to operate the plunger 42. A rheostat 46 has a rotatable stem 4'I arranged to be turned by means of the rack 48 and pinion 49, the rack 48 forming a part of the rack plunger 42. In that way, assuming there is a certain setting for the speed of the series-wound motor 22, the operator may be raising the plunger 42 change the speed for whatever interval he may desire, as for example, in making a set-up for a new job. A screw 50, which has a radially enlarged head 5I projecting into an elongated notch 52 in one side of the rack plunger 42 to limit the downward movement of the plunger and accordingly variably predetermine the top speed of the motor 22, is set for a fixed top speed, and lower speeds are obtained by movement of the plunger 42 upwardly, accomplished either manually or by dog operation, such upward movement causing a change in the setting of the rheostat 46. Obviously, one long dog with suitable steps on it will suffice to speed up and slow down the feed movement of the carriage I6 by causing corresponding movement of the plunger 42. The cam plunger 44 operates the push buttons 53, 54 and 55 of three limit switches 56, 51 and 58, respectively, which control the starting and stopping of the motors 2| and 22 and the reversing of motors 2i. Dogs for operating the plungers 42 and 44 are provided in the two lines on the base or bed 6 of the machine as previously mentioned for movement of the carriage I6 and control box 4I relative thereto, such dogs being indicated at 59, 60, 6I and 62 in Fig. 1. The dog 62 is the one long dog" mentioned above.

The operation of the electrical control mechanism can be best understood by reference to the positions marked in Fig. 1, and by reference to the wiring diagram, Fig. 5, and is as follows:

Position #L -The carriage I6 is at a standstill after completion of a cycle, ready for the start of the next cycle. The operator rst depresses the push button 63 to operate the contacter 64 through energization of the coil 65, thereby closing interlocks 66, 6l and 68, and also closing the circuit through the spindle motor I1 at 69, to place the machine in readiness to start the cycle. To start the cycle, the operator next depresses the starter button 1I), thus operating the contacter 1I through energization of the coil l2, closing interlocks 13 and I4 and completing the circuit through the motor 2I at 'I5 for rapid approach movement of the carriage I6. The motor 22 also has a circuit completed through it by reason of the closing of the interlock and the consequent energization of coil 16. In that way the nut I4 is turned, thus increasing the speed of approach movement of the carriage.

Position #2.-Limit switch 56 is closed by f movement of plunger 44 by dogy 59, so as to permit the carriage I6 to be returned during approach movement by the operator's depressing a push button 11. This is for emergency purposes only.

Position #3.-Limit switch 5l is opened at the end of the rapid approach movement by movement of the plunger 44 by dog 6D. The coil I2 of contactor 1I is thereby de-energized and motor 2I is stopped, but the feed motor 22 continues to run for the feed movement of the carriage from position #3 to position #4, because interlock 'I8 keeps the coil 'I6 energized while interlock I4 is open. During this feed movement, the dog 62 operates plunger 42 to regulate rheostat 46 and accordingly regulate the speed of motor 22. At any point in the feed movement the speed may be stepped up or down quickly or gradually as required. Thus, dog 62 has a rise on the end to cause plunger 42 to be raised accordingly for a slowing up gradually' of the speed of motor 22 for a corresponding gradual slow up of the carriage I6 at the end of the feed movement, as may be desired, for example, in a facing operation.

Position #4.-At this position, limit switch 58 is closed by means of plunger 44 moved by dog 6I, and when the carriage I6 is run up against the positive stop 39 current in the windings of motor 22 is increased, causing the work relay 'I9 to close contacts and thus energize coil 8I of contacter 82 and start motor 2| operating in the reverse direction.

Alternatively, in this position, selector switch 83, which may be provided in the control box 4| and suitably operated, let us say by the dog 62, is closed to permit current flow from 8| to 85, so that when switch 58 is closed, as above described, coil 8| of contacter 82 is energized and motor 2| is started operating for rapid return of the carriage I6. In either kind of operation, when contacter 82 is closed interlock I6 is opened and coil 'i6 de-energized thereby opening contacter 8l and stopping feed motor 22. Coil 8| is kept energized during rapid return by interlock 88 until limit switch 58 is opened. When that occurs at the end of the rapid return movement, motor 2| stops and the machine is ready for a new cycle.

It is believed the foregoing description conveys a good understanding of the objects and advantages of our invention. The appended claims have been drawn to cover all legitimate modifications and adaptations.

We claim:

1. In a machine tool feed mechanism, the combination with a bed and a carriage movable thereon, of a feed screw disposed parallel to the direction of carriage movement and supported at one end for rotation on the bed and having an elongated splined portion and an elongated threaded portion, a splinedsleeve on the carriage slidable on the splined portion, a nut threaded on the threaded portion of the feed screw and mounted for rotation in fixed spaced relationship to the sleeve on the carriage, a reversible motor for driving the splined sleeve, another motor on the carriage for driving the nut, a control box on the carriage movable with it relative to dogs on the bed, switches in the control box controlling the starting and stopping of said motors and the reversal of the first mentioned motor, means operable by one or more of said dogs in the movement of the carriage for automatically operating said switches in a predetermined relationship for a predetermined cycle, a rheostat in the control box for regulating the speed of the second motor, and means operable by one or more of said dogs for operating said rheostat in the movement of the carriage for automatically operating said rheostat for a predetermined cycle.

2. In a machine tool feed mechanism, the combination with a, bed and a carriage movable thereon, of a feed screw disposed parallel to the direction of carriage movement and supported at one end for rotation on the bed and having an elongated splined portion and an elongated threaded portion, a splined sleeve on the carriage slidable on the splined portion, a nut threaded on the threaded portion of the feed screw and mounted for rotation in fixed spaced relationship to the sleeve on the carriage, a motor on the carriage for driving the splined sleeve, another motor on the carriage for driving the nut, and means operable in the movement of the carriage for automatically controlling the operation of the motors and thereby the driving of the feed screw andnut through a. predetermined cycle, said means including a rheostat for varying the speed of the second motor.

3. In a machine tool feed mechanism, the combination with a stationary bed member and a relatively recriprocable carriage member, of a feed screw disposed parallel to the direction of carriage movement and supported at one end for rotation on one of said members and having an elongated splined portion and an elongated threaded portion, a splined sleeve slidable on the splined portion and a nut threaded on the threaded portion of the feed screw, a reversible motor for driving the splined sleeve, another motor for driving the nut, a, control box on the carriage movable with it relative to dogs on the bed, switches in the control box controlling the start.- ing and stopping of said motors and the reversal of the first mentioned motor, and means operable by one or more of said dogs in the movement of the carriage for automatically operating said switches in a predetermined relationship for a predetermined cycle.

4. In a machine tool feed mechanism, the combination with a stationary bed member and a relatively reciprocable carriage member, of a feed screw disposed parallel to the direction of carriage movement and supported at one end for rotation on one of said members and having an elongated splined portion and an elongated threaded portion, a splined sleeve slidable on the splined portion and a nut threaded on the threaded portion of the feed screw, a, reversible motor for driving the splined sleeve, another motor for driving the nut, a control box on the carriage movable with it relative to dogs on the bed, switches in the control box controlling the starting and stopping of `said motors and the reversal of the first mentioned motor, means operable by one or more of said dogs in the movement of the carriage for automatically operating said switches in a prede.- termined relationship for a predetermined cycle,

' a rheostat in the control box for regulating the speed of the second motor, and means operable by one or more of said dogs for operating said rheostat in the movement of the carriage for automatically operating said rheostat for a predetermined cycle.

5. In a machine tool feed mechanism, the combination with a stationary bed member and a relatively reciprocable carriage member, of a feed screw disposed parallel to the direction of carriage movement and supported at one end for rotation on one of said members and having an elongated splined portion and an elongated threaded portion, a. splined sleeve on the carriage slidable on the splined portion, a, nut on the carriage threaded on the threaded portion of the feed screw, a motor on the carri-age for driving the splined sleeve, another motor on the carriage for driving the nut, and means operable in the movement of the carriage for automatically controlling the operation of the motors and thereby the driving of the feed screw and nut through a predetermined cycle, said means including a rheostat for varying the speed of the second motor.

6. In a machine tool feed mechanism, the combination with a bed and a carriage movable thereon, of a feed screw disposed parallel to the direction of carriage movement and supported at one end for rotation on the bed, means adapted for driving the feed screw in either direction, a reversible motor for driving said means, a nut threaded on the feed screw, a motor for driving the nut, a control box on the carriage movable with it relative to dogs on the bed, switches in the control box controlling the starting and stopping of said motors and the reversal of the first mentioned motor, means operable by any one or more of said dogs in the movement of the carriage for automatically operating said switches in a predetermined relationship for a predetermined cycle, a rheostat in the control box for regulating the speed of the second motor, and means operable by one or more of said dogs for operating said rheostat in the movement of the carriage for automatically operating said rheostat for a predetermined cycle.

7. In a machine tool feed mechanism, the combination with a bed and a carriage movable the nut, and means operable in the movement of the carriage for automatically controlling the operation of the motors and thereby the driving of the feed screw and nut through a predetermined cycle, said means including a rheostat for varying the speed of the second motor.

8. In a machine tool, the combination with a bed and a carriage movable thereon, of a feed mechanism, a reversible motor and a driving train for driving the feed mechanism in either direction at traverse speeds, another motor and an independent driving train for driving the feed mechanism at variable speeds, and means operable in the movement of the carriage for automatically controlling the starting and stopping of the two motors and the reversal of the first motor and the speed of operation of the second motor through a predetermined cycle.

9. 4In a machine tool, the combination with a bed and a carriage movable thereon. of a feed mechanism, a reversible motor and a driving train for driving the feed mechanism in either direction at traverse speeds, another motor and an independent driving train for driving the feed mechanism at variable speeds, a control box on the carriage movable with it relative to dogs on the bed, switchesin the control box controlling the starting and stopping of said motors and the reversal of the first mentioned motor, and means operable by one or more of said dogs in the movement of the carriage for automatically operating said switches in a predetermined relationship for a predetermined cycle.

10. In a machine tool, the combination with a bed and a carriage movable thereon, of a feed mechanism, a reversible motor and a driving train for driving the feed mechanism in either direction at traverse speeds, another motor and an independent driving train for driving the feed mechanism at variable speeds, a control box on the carriage movable with it relative to dogs on the bed, switches in the control box controlling the starting and stopping of said motors and the reversal of the rst mentioned motor, means operable by one or more of said dogs in the movement of the carriage for automatically operating said switches in a predetermined relationship for a predetermined cycle, a rheostat in the control box for regulating the speed of the second motor, and means operable by one or more of said dogs for automatically operating said rheostat in the movement ofthe carriage for a predetermined cycle.

11. An electrical control device for use on a machine tool carriage or the like comprising a housing, a plurality of switchesin said housing having push buttons arranged in a row, a cam plunger reciprooable in said housing relative to said push buttons, said switches being adapted for controlling the starting and stopping of a plurality of motors and the reversing of at least one motor, and said plungers being adapted to be reciprocated by dogs in the movement o1' the carriage, a rheostat in said housing for controlling the speed of operation of at least one motor, said rheostat having a rotary shaft, rack and pinion means for turning said shaft. and another plunger reciprocable in said housing carrying said rack, said last mentioned plunger being adapted to be reciprocated by dogs in the movement of the carriage.

12. An electrical device as set forth in claim 11 wherein said last mentioned plunger normally tends to gravitate toward one extreme position and is moved by dogs in the opposite direction.' said device including a screw threaded adjustment for predetermining the limit position of s said plunger in itsmovement by gravity whereby to accordingly predetermine the extreme motor speed.

13. In a machine tool, the combination with a bed and a carriage movable thereon and carrying a motor driving a work spindle, of a feed mechanism, a rapid reversible motor and a driv-l ing train for driving the feed mechanism in either direction at traverse speeds. dogs on the bed for operating control means on the carriage for automatically controlling the starting, stopping and reversing of said motor in a predetermined cycle, another motorand an independent driving train for driving the feed mechanism in feed movements of the carriage, and dog means on the bed operating control means on the carriage in the movement of the carriage for automatically controlling the starting, stopping and variation in speed of operation of the last mentioned motor in a predetermined cycle.

14. In a machine tool, the combination with a bed and a carriage movable thereon and carrying a motor driving a work spindle, of a feed mechanism, a rapid reversible motor and a driving train for driving the feed mechanism in either direction at traverse speeds,'dogs on the bedfor operating control means on the carriage for automatically controlling the starting, stopping and reversing of said motor in a predetermined cycle, another motor and an independent driving train for driving the feed mechanism in feed movements of the carriage, means controlling the starting and stopping of said last mentioned motor, and a single elongateddog on the bed for operating control means on the carriage in the movement thereof for automatically varying the speed of the last mentioned motor in a predetermined Cycle.

AXEL F. REHNBERG. JOHN NELSON.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS s Date v Certicate of Correction Patent No. 2,520,014 August 22, 1950 AXEL F. REHNBERG ET AL.

It is hereby certified that error appears'in the printed specification of the above numbered patent requiring correction es follows:

Column 5, line 36, after the Word motor insert on the carriage;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office. Signed and sealed this 5th day of December, A. D. 1950.

[SNL] THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

